Using single molecule magnetic tweezers to study the mechanical unfolding of proteins

Single molecule magnetic tweezers rely on tethering a biomolecule between a glass surface and a paramagnetic bead. Force is applied by controlling the magnetic field ontop of the bead, and the molecular extension is measured from the relative change between the same paramagnetic bead and the surface. In the first part, I will talk about the working principles of magnetic tweezers and its application to proteins. Under a force vector, protein domains unfold in a probabilistic manner. This mechanical unfolding is followed by an entropic extension of the polypeptide chain, due to the force vector. This unfolding and extension of a protein under force represents a poorly understood gain-of-function for proteins in vivo. In the second part of my talk, I will present data obtained using magnetic tweezers from protein systems that operate in vivo under force and where mechanical unfolding can act as a signaling pathway. These systems are relevant for muscle contraction, cellular mechanotransduction and bacterial adhesion.